High temperature stability and deposition control are key performance factors for high performance lubricants. In aviation turbine engines, the bulk oil temperatures can be as high as five hundred degrees Fahrenheit. In such applications, even the best commercial oils can sometimes experience thermal degradation. As a result, the degraded oil may cause filter plugging due to deposits formed on hot spots of the high temperature operating engines. This is particularly the case for lubricating oils used in jet aircraft where wide temperature ranges and extreme operating conditions are likely to be encountered. Proper lubricating of aircraft gas turbines, for example, requires the ability to function at bulk oil temperatures as low as minus sixty-five degrees Fahrenheit to as high as five hundred degrees Fahrenheit. The thermal degradation of high performance lubricants leads to the production of sludge, which may also damage equipment parts, reduce performance, and increase maintenance. The most widely used base stocks are PAO, synthetic hydrocarbon, and hindered polyol esters made mostly from linear fatty acids. These typically have a maximum operating temperatures of from three hundred ninety-two to four hundred sixty-four degrees Fahrenheit. Somewhat higher performance lubricants are based on polyphenyl ethers and perfluoropolyalky ethers, which can be used up to about five hundred thirty-six to five hundred seventy-two degrees Fahrenheit. However, these fluids are very expensive and have low temperature flow and metal corrosivity problems.
While engine temperatures continue to increase to enhance operating efficiency, reliable, light weight, new classes of base stock fluids that are more economical than the currently used polyphenyl ethers and perfluoropolyalkyl ether are needed.